<!DOCTYPE html>
<html>
  <head>
    <title>HTML 简介</title>
    <meta charset="utf-8" />
  </head>
  <body>
    <h1>我是一级标题</h1>
    <h2>我是二级标题</h2>
    <h3>我是三级标题</h3>
    <h4>我是四级标题</h4>
    <h5>我是五级标题</h5>
    <h6>我是六级标题</h6>
  </body>
</html>